Hello Dave
As you are probably aware, the lower the number, the hotter the plug so I am in the same mind of thinking that the "4 "
may be a little too hot.
I was led to believe that the B6HS was the correct plug for our type of head but with mine, I found that they oiled up quite quickly. The change to a B5HS stopped that problem immediately for me but I will certainly try a BP5HS next time as Ian suggests as I have a lot of respect for his knowledge of these things.
I also always buy mine on Ebay and usually pay around the £6 mark with delivery included. (That's for 4 by the way).
Hope this helps a little.
Graham.

(10-07-2018, 07:16 PM)Graham Honnor Wrote: Hello Dave
As you are probably aware, the lower the number, the hotter the plug so I am in the same mind of thinking that the "4 "
may be a little too hot.
I was led to believe that the B6HS was the correct plug for our type of head but with mine, I found that they oiled up quite quickly. The change to a B5HS stopped that problem immediately for me but I will certainly try a BP5HS next time as Ian suggests as I have a lot of respect for his knowledge of these things.
I also always buy mine on Ebay and usually pay around the £6 mark with delivery included.
Hope this helps a little.
Graham.

The BP5HS is definitely the one to go for for a normal Austin seven.
For those with 18mmm plugs I have found that the D21 is a good bet especially with mag cars.

Thanks for that Nick, it's good to know you'd recommend them as well.
Having never used a projected plug before, I presume the length is the same as a normal one is it, and there's no
chance of it protruding into the head too far?
Sorry if that's a daft question, and for hijacking your thread John.
Graham.

(12-07-2018, 02:27 PM)John Mason Wrote: This might seem a stupid question but if you need a 22 MM spanner to tighten/ untighten your spark plugs does this mean they are 22 MM plugs.

John Mason

Stop me if I'm missing something, but plug 'size' is the size (nominal diameter) of the screw thread, not the 'across flats' nut size.
Just as a 6mm bolt is 10mm across flats, for example, and needs a 10mm spanner to undo it.

I have been reading the feedback about different spark plugs with great interest. Does anyone have any experience of running different plugs in 'non standard' cylinder heads? My special is fitted with a Supaloy head. At the moment it has Champion L86C plugs. Would there be much benefit in fitting 'hotter' plugs such as the NGK B5HS or BP5HS?

I have also followed this information on Spark plugs with interest. Are all the ones mention 14mm plugs?
I use 18mm plugs on my Nippy but I suppose the same rules apply. Mine are always sooty.
Just that I get the impression that the choice of 18mm plugs is rather limited. And more expensive, particularly out here in Switzerland.